This invention relates to the field of water disinfection, and specifically to disinfection of drinking water in remote locations where conventional disinfecting apparatus and materials are not available.
Failure to properly disinfect water supplies is one of the most serious problems affecting the health of the residents of third world countries, in particular residents of small towns, rural areas and marginal urban areas. Disinfection of drinking water is a fundamental health measure, and whenever carried our reliably and adequately, it has assured the health of users of the water supply.
There are more than twenty diseases related to drinking water supply. Debilitating and in some cases deadly, the diseases impose a terrible economic and physical handicap on everyone involved, especially upon the poor who can least afford it. The most serious and frequent of these diseases, to a very large extent, can be prevented through adequate disinfection of water supplies.
Numerous studies have been performed over the past fifty years of the benefits of disinfection, but two of the most recent are particularly significant. One study, an eight year study by Bersch and Osorio, found an inverse relationship between the levels of residual chlorine in water supplies and the rates of diarrhea among children under five years of age. In another study, a 1981 pilot project compared 300 families in West Bengal, India that received disinfected drinking water with 300 families that did not. All of the factors were determined to be essentially the same. Over a nine month period, there was an 80% reduction in the incidents of diarrhea among children receiving the disinfected water as compared to only a 5% reduction among the other children.
In situations where water is the predominant vehicle for transmission of typhoid, paratyphoid, cholera, diarrhea, hepatitis and giardiasis, adequate levels of disinfection and adequate contact time will reduce the incidents of disease, so that the health benefits of more reliable, simpler and cheaper disinfection are obvious.
Although many conventional methods of disinfection are available throughout the world, over 75% of all disinfection facilities in third world countries have failed to provide continuous and adequate disinfection despite more than twenty years of effort to develop human resources, institutions, an supporting infrastructures. The commonly cited reasons for the failure of disinfection are:
1. Undependable or unavailable supply of chemicals; PA1 2. Unavailability of spare parts; PA1 3. Operational requirements too complex for local operators; PA1 4. Repair of equipment too complex for local operators; PA1 5. Inadequate infrastructure to support the purchase, transport and storage of chemicals, spare parts and supplies; PA1 6. User dissatisfaction with widely varying chlorine levels; PA1 7. Difficulties involved with local storage, handling, mixing and dosing of chemicals; PA1 8. Limited durability of equipment; PA1 9. Insufficient operator training and experience, as well as inadequate basic education; and PA1 10. Inadequate safety considerations.
A number of alternate technologies employing ozonation, ultra violet light, halogenated resins, radiation, ionization, chlorine dioxide, chlordanes, and appropriate technologies for hypochlorination have been introduced to overcome the above problems, but these haven't circumvented the major causes of the failures. Some of the alleged cures have even added to the failures. Generally, the majority of advancements in disinfection have been aimed primarily in solving problems encountered in industrialized countries and have not been directed to solve the specific and different problems of disinfection in developing countries.
Disinfecting devices suitable for use in small towns and rural areas of developing countries should be simple to operate and maintain and avoid chemical and mathematical calculations which are beyond the capability of local operators. The equipment should also be durable and easy to repair and use readily available chemicals. Finally, the equipment should be useable over a wide range of physical and chemical conditions.